The invention relates to a pressure infusion apparatus comprising a drive which exerts a periodic pressure movement via a delivery mechanism (such as rotor or finger peristalsis) advancing during delivery on a section of a flexible tube in which the medium to be delivered is disposed, and a pressure means stationary during the delivery, such as pressure plate, stator or tube plate.
Pressure infusion apparatuses are used for pumping infusion fluids or solutions which are disposed in a supply vessel into the vein of a patient at a rate desired in accordance with the particular therapy. The pressure infusion apparatus is disposed at a connecting tube between the supply vessel and a cannula. Pressure infusion apparatuses of various constructions are known.
One known construction comprises a stator and a rotor driven by a motor, with a flexible pump tube or hose being clamped between the rotor and stator. By the rotation of the rotor the hose or tube is continuously compressed in the direction toward the patient, and the infusion solution disposed in the tube is thereby being pumped at a predetermined rate into the vein.
Such a pressure infusion apparatus is known, for example, from Carson, et al. U.S. Pat. No. 4,184,815 (Jan. 22, 1980). To insert the tube the rotor must be turned by hand into a predetermined position in order to prevent squeeze rollers arranged on the rotor from obstructing insertion. After a portion of the tube has been placed between the rotor and stator the rotor must be further turned by hand, with the first squeezer roller then already pressing against the tube. For this purpose the user (physician, nurse, patient, etc.) must exert a specific force.
In a peristaltic pump as is known from Clemens U.S. Pat. No. 4,025,241 (May 24, 1977), for example, the stator must be pressed away from the rotor against the force of two springs for the tube segment to be inserted.
Peristaltic pumps may be equipped with a finger peristalsis mechanism in which a large number of fingers or pump rams are arranged in a straight line adjacent each other. The infusion tube filled with the medium to be delivered is clamped between the free ends of the pump rams and a pressure plate. The solution in the infusion tube is delivered by a peristaltic movement of the pump rams. With this construction as well the user must press a pressure plate away from the pump rams against the action of a spring in order to insert the infusion tube.
Finally, statorless roller pumps are also known in which the tube is secured in a tube plate in such a manner that the tube segment forms a loop. For inserting the tube segment the loop must be placed over the rotor and the tube plate inserted into a holder. Loop size and rotor/holder spacing are adapted to each other in such a manner that on insertion of the tube plate into the holder the tube is compressed by the rollers of the rotor. This pretensioning of the tube segment also requires the application of a certain force on the part of the user.
In all known prior pressure infusion apparatuses the application or pressure means for the tube must be lifted off the delivery mechanism or applied by mechanical work on the part of the user. This is done either by direct gripping of the application or pressure means or delivery mechanism or by indirect "gripping" with the aid of levers or knobs.
It is also known to intermediately store part of the mechanical work applied by the user on opening or closing the pressure application means in order then to enable closure or opening of the pressure means by the application of less force. In each case however it is the user who must do the mechanical work.